In many of the airbag apparatuses that are installed on the side of the driver's seat, an airbag module is assembled integrally with an interior side of the horn operation portion of the steering wheel. In this case, a horn block in which the horn operation portion and the airbag module are integrally assembled, is attached to a steering wheel main unit, which is supported by a steering shaft, by means of attachment pins.
As a structure of the steering wheel of this type, there is known a structure in which a rubber elastic body is interposed in a part of the attachment pin and in which the horn block and the rubber elastic body are used to form a dynamic damper for suppressing a vibration of the steering wheel (for example, see Patent Document 1).
In the steering wheel structure described in Patent Document 1, an attachment pin includes: a first pin block that is locked on a horn block side; a second pin block that is locked on a steering wheel main unit side; and a rubber elastic body that connects between the first pin block and the second pin block, wherein the second pin block is configured to be capable of displacing in an axial direction with respect to the steering wheel main unit by a predetermined stroke. Between the steering wheel main unit and the horn block, there are provided horn contacts that activate the horn when the horn block is pushed in by a set stroke or longer. Between the steering wheel main unit and the second pin block, there is interposed a horn spring that biases the horn block toward a default position.
In the steering wheel that adopts this structure, when a vibration such as an engine vibration or a travelling vibration is input to the steering wheel, the mass of the horn block and the rubber elastic body of the attachment pin function as a damper mass and a spring of a dynamic damper, to thereby suppress an input vibration through resonance of the horn block. Furthermore, when the horn block is pushed in in a steering wheel main unit direction, the attachment pin moves in its stroke in the axial direction with the compressive deformation of the horn spring. Subsequently, at the time when the horn block is pushed in by the set stroke or longer, the horn is activated through contact between the horn contacts.